WO2001019515A1

WO2001019515A1 - Catalyst with discharge electrode or carrier

Info

Publication number: WO2001019515A1
Application number: PCT/JP2000/006043
Authority: WO
Inventors: Akira Mizuno; Saburo Tanaka; Masayoshi Ichiki; Kazuhiro Kondo; Michitaka Furubayashi; Shuji Hamano
Original assignee: Hitachi Zosen Corporation
Priority date: 1999-09-09
Filing date: 2000-09-06
Publication date: 2001-03-22
Also published as: KR20020034184A; CA2384708A1; EP1224973A1

Abstract

A catalyst with a discharge electrode effectively applicable to a method for efficiently decomposing harmful substances such as dioxin in exhaust by plasma discharge, or a carrier for catalyst is disclosed. The catalyst with a discharge electrode or the carrier has a dotted pattern of electrode, a linear electrode which may intersect itself, or a bar-like electrode at least on one side of the plate-like or sheet-like catalyst or the carrier. The plate-like or sheet-like catalyst or carrier may be a cloth, board, or paper catalyst or carrier. The electrode is preferably formed at least on one side of the plate-like or sheet-like catalyst or carrier by printing conductive printing ink containing a metal such as silver, sintering a metal powder, vapor-depositing a metal, or sputtering a metal. The conductive ink may be pasty. A preferable shape of the electrode is comb-teeth.

Description

Description Catalyst or carrier with discharge electrode Technical field

The present invention relates to a catalyst or a carrier for a catalyst provided with a discharge electrode, and a catalyst or a carrier for a catalyst provided with a discharge electrode and a photocatalyst disposed between, at, or outside thereof. The present invention relates to a catalyst block provided with a discharge electrode. The present invention also relates to a method and an apparatus for decomposing harmful substances such as dioxins in exhaust gas discharged from refuse incinerators, various boilers, diesel engines, and the like by plasma discharge. Background art

Conventionally, it has been known that photocatalysts have strong oxidizing power and can be used to oxidize and decompose dioxins. However, in order for the photocatalyst to work effectively, it is necessary to irradiate the surface of the catalyst particles with photons of a predetermined frequency. For this reason, it is difficult to irradiate individual particles with a sufficient amount of photons in a catalyst packed bed in which a large number of catalyst particles are packed in a reaction vessel, and photocatalysts do not work effectively.

Therefore, it is possible to remove harmful substances in exhaust gas by using the high oxidation / reduction power of the photocatalyst, but it is difficult to uniformly irradiate the surface of catalyst particles with high energy ultraviolet rays. Therefore, it is impossible to fill a limited space with a large amount of catalyst.The reaction vessel is large compared to, for example, a denitration reactor. Since no activity can be obtained and the reaction rate of exhaust gas passing therethrough is low, They disliked that a high harmful substance removal rate could not be obtained as a whole. A first object of the present invention is to provide a method and an apparatus for efficiently decomposing harmful substances such as dioxins in exhaust gas by plasma discharge in order to solve the above problems.

A second object of the present invention is to provide a catalyst having a discharge electrode or a carrier for a catalyst, which can be effectively applied to a method for efficiently decomposing harmful substances such as dioxins in exhaust gas by plasma discharge. To provide a catalyst block equipped with a discharge electrode ^) Disclosure of the invention

The first invention according to the present invention relates to a catalyst or a carrier with a discharge electrode.

The catalyst or carrier with a discharge electrode according to the first aspect of the present invention may have at least one side of a plate-shaped or sheet-shaped catalyst or carrier, and may have a dotted or crossed linear shape. Is provided with a rod-shaped electrode.

The plate-like or sheet-like catalyst or carrier includes a cross-like, board-like, paper-like catalyst or the like.

The electrodes are preferably printed on at least one side of a plate or sheet of catalyst or carrier with a conductive printed ink containing a metal such as silver, copper, and in some cases a solder alloy. Formed by sintering metal powder, sintering metal, or depositing or sputtering metal. The conductive ink may be in the form of a paste.

The preferred electrode shape is a comb shape. Comb-shaped electrodes are on the front and back surfaces of the catalyst or carrier, and each comb tooth on the back electrode is a front electrode It is preferable that they are formed so as to be opposite to the respective comb teeth and to be positioned between the respective comb teeth of the surface electrode, that is, to be staggered.

The preferred catalyst is a catalyst material or a porous material supporting the catalyst material between matrix ceramic fibers made of a plate-like or sheet-like preform made of ceramic fibers. The carrier particles are dispersed and held. The catalytic substance is an oxide of a metal such as vanadium, tungsten, molybdenum, or titanium, or a metal or an oxide thereof such as gold, silver, platinum, rhodium, palladium, or ruthenium. May be.

The preferred carrier is a porous carrier particle dispersed and held between matrix ceramic fibers composed of a plate-like or sheet-like preform composed of ceramic fibers. It was made. The porous carrier may be alumina, silica, silica / alumina, titania, zeolite, perconia, zinc oxide, or the like.

The present invention utilizes a space discharge caused by application of a high voltage, a surface current generation on an insulator surface, and the like to cause charge / polarization of a solid catalyst surface, ionization / electronic polarization of a reactant, etc. It manifests or promotes.

When semiconductor particles are filled between a pair of electrodes and a high voltage is applied between the electrodes, the electrons run on the particle surface while ionizing the surrounding gas (surface current), and at the same time, excite the electrons constituting the solid crystal to ionize. I do. When the excited electrons return to the ground state, they emit light that is peculiar to atoms (mostly ultraviolet light). In addition, when high-energy electrons collide with a semiconductor crystal, a plurality of conduction band electrons are repelled, and holes, which are considered to be the basis of the photocatalytic activity, also appear. Such a discharge state is called a plasma discharge. As described above, when a voltage required for discharging is applied between the electrodes, the activity of the photocatalyst can be excited without irradiating ultraviolet light from outside.

However, if such a discharge continues and the gas phase and solid phase ionization progress, the discharge shifts to arc discharge with remarkable heat generation, which leads to thermal deterioration of the catalyst and lower energy efficiency, which is not preferable. . Therefore, it is desirable to lower the potential between the electrodes before the discharge shifts to arc discharge and terminate the plasma discharge. That is, it is desired to apply a high AC voltage or a pulse voltage to the electrode. In this case, it is necessary to increase the frequency of AC voltage or pulse voltage in order to maintain high energy efficiency and increase the discharge amount.

A reactor utilizing such a phenomenon can be suitably used for oxidative decomposition of dioxins in waste gas from a garbage incinerator. However, when the reaction gas contains solids such as dust and ash, they not only accumulate on the particle bed and cause a rise in the flow resistance of the reaction gas, but also hinder effective discharge. It is necessary to remove the reactant gas sufficiently upstream of the reactor in order to prevent a short circuit between the electrodes.

The catalyst or carrier with a discharge electrode according to the first aspect of the present invention is formed on the surface of a plate-like or sheet-like catalyst (including cross-like, board-like, paper-like, etc.) or dot-like or cross-like surface. A linear or rod-shaped electrode may be provided to generate a discharge that penetrates the plate in the thickness direction and emits ultraviolet light from the entire plate or sheet catalyst or catalyst carrier. It is possible.

That is, the electrons emitted from the cathode move to the anode as a semiconductor surface current, ionize the solid surface, and generate a large number of holes. At the same time, the surrounding gas is ionized, and gaseous atoms and Makes the outer electrons of the molecule excited. When electrons in the excited state return to the ground state, they emit ultraviolet light unique to the substance. Holes are generated in the semiconductor due to the energy of ultraviolet light. Oxidation activity is expressed by the action of these holes.

The voltage applied to the electrodes is sufficient for the space discharge voltage (SKVZ mm) or less, but higher voltages may be applied to obtain high ultraviolet light emission and high surface activity. It is possible. The lower limit of the applied voltage is the plasma discharge starting voltage, and the higher limit is the voltage at which breakdown occurs between the electrodes. These values are appropriately determined depending on the type of the semiconductor, the composition of the atmospheric gas, the temperature, and the like.

The electron flow tends to concentrate in a path with a short distance between the electrodes. In addition, the electron flow tends to concentrate on the area where the various ions generated are present. Therefore, the distance between the electrodes must be strictly uniform in order to uniformly generate a discharge that passes through the plate-shaped catalyst or the catalyst carrier.

In a structure in which electrodes are arranged on both sides of a plate-shaped or sheet-shaped catalyst or catalyst carrier so that the distance between the electrodes is uniform, the resistance of electrons passing through the catalyst or catalyst carrier and the surface of the catalyst or catalyst carrier are reduced. Since the resistance to the movement of the electrons is significantly different, the variation in the distance between the electrodes is not so affected, and almost uniform ultraviolet light emission is observed on the entire surface of the catalyst or the catalyst carrier.

In consideration of the above points, the first invention is, specifically, a comb-shaped electrode on both sides of a plate-like or sheet-like catalyst or a catalyst carrier in a staggered manner on the front and back of the plate ( For example, a catalyst or a catalyst carrier provided with a discharge electrode, which is arranged by being shifted by 1 Z 2 of a comb tooth interval, is provided.

The smaller the thickness of the teeth of the comb-shaped electrode, the better. In the case of a sheet-like catalyst or catalyst carrier, 0.1 to 2 mm is desirable from the viewpoint of reliability against disconnection. In order to manufacture a comb-shaped electrode, a method in which a conductive printing ink is printed on both front and back surfaces of a catalyst or a catalyst carrier is preferable from the viewpoint of manufacturing cost, accuracy of inter-comb spacing, and the like.

As a plate or sheet catalyst or catalyst carrier, a plate or sheet ceramic ceramic fiber preform (sheet, paper, cross, It is preferable that a catalyst or catalyst carrier fine particles are dispersed and held between matrix fibers having a board shape or the like. A catalyst or a catalyst carrier having such a structure has a relatively large amount of space inside, and has a high diffusibility of the reactants, and the ultraviolet radiation efficiency is increased by the excitation of the gas existing in the space. I do.

The catalyst or catalyst carrier equipped with a discharge electrode with the above configuration exhibits high catalytic activity in the exhaust gas stream, and purifies exhaust gas by oxidizing and decomposing dioxins, oxidizing hydrocarbons, and oxidizing NO. Works effectively. In this case, since the catalyst or the catalyst carrier is in the form of a plate or a sheet, it is difficult to block due to solids such as dust, and is directly discharged to a gas stream in which the solids such as dust flow. Therefore, dust is not easily charged, and dust is not easily adhered to the catalyst surface or electrodes.

A second invention according to the present invention relates to a catalyst block with a discharge electrode.

The catalyst block with a discharge electrode according to the second invention is a plate or sheet having at least one surface of a dot-shaped or crossed linear or rod-shaped electrode. And a photocatalyst disposed between the electrodes or the catalyst and the carrier and Z or on the outside. In the above catalyst block, the plate-like or sheet-like catalyst or carrier includes a cross-like, board-like, paper-like, or the like. A preferred carrier with electrodes is a porous carrier particle dispersed and held between matrix ceramic fibers composed of a plate-like or sheet-like preform made of ceramic fibers. It is a thing. The porous carrier may be alumina, silica, silica, alumina, titania, zeolite, zirconia, zinc oxide, or the like.

In the above-mentioned catalyst block, a preferred catalyst with an electrode and a photocatalyst are formed between a matrix ceramic fiber composed of a plate-like or sheet-like preform made of ceramic fiber. In addition, a catalyst material or porous carrier particles carrying the same are dispersed and held. The photocatalyst may be, for example, a granular catalyst, a flat plate or a corrugated plate. The catalyst substance is an oxide of a metal such as vanadium, tungsten, molybdenum, or titanium, or gold, silver, platinum, rhodium, or phosphorus. Metals such as radium and ruthenium or oxides thereof may be used.

In the above catalyst block, the preferred electrode is to print a conductive printed ink on at least one side of a plate or sheet of catalyst or carrier, or to sinter a metal powder. Or formed by vapor deposition or sputtering of metal.

The preferred shape of the electrode is a comb shape, and the comb-shaped electrode is preferably on each of the front and back surfaces of a plate or sheet-like catalyst or carrier, and each comb tooth of the back surface electrode is a comb of the front surface electrode. It is formed so as to be opposite to the teeth and to be located between the respective comb teeth of the surface electrode.

Preferred catalyst blocks are those with a plate or catalyst with electrodes. The photocatalyst is corrugated, and the catalyst or carrier with electrodes and the photocatalyst are alternately overlapped to form a honeycomb shape as a whole. In such a honeycomb catalyst block, preferably, each end in the gas flow direction of the plate-shaped catalyst with an electrode or the carrier protrudes from the corrugated photocatalyst, and a comb-shaped electrode is formed at the protruding end. Each of the back portions is connected via an electrode connecting member. As the electrode connecting member, a conductive material having a shape such as a wire, a bar, a shaft, or a belt is used. Adjacent electrodes are connected to each other by a structure in which the electrode connecting member penetrates or crosses each back portion of the comb-shaped electrode at the protruding end in a skewered manner. It is preferable to provide a plurality of electrode connecting members in consideration of the possibility that electrical contact may be deteriorated due to oxidation of the electrodes and the electrode connecting members when the catalyst is used.

In the catalyst or carrier with a discharge electrode according to the first invention, or the catalyst block with a discharge electrode according to the second invention, a voltage of 0.03 to 50 KV per 10 mm between electrodes is applied between a pair of electrodes. By applying a voltage of 4 to 200 KHz and causing a discharge between the two electrodes via a catalyst or a carrier, the catalyst or the carrier with an electrode can be activated.

The catalyst or carrier with a discharge electrode according to the first invention, or the catalyst block with a discharge electrode according to the second invention is, for example, installed in a gas flow path, and a voltage is applied between a pair of electrodes under the above conditions. Is applied between the two electrodes to cause discharge through the catalyst or carrier, thereby activating the catalyst or carrier with electrodes and being used in a gas catalytic reaction method in which the target components in the gas are contacted and reacted. You.

Specific examples of the gas catalytic reaction method include a catalyst or carrier with a discharge electrode according to the first invention, or a catalyst or carrier with a discharge electrode according to the second invention. A catalyst block in the flue gas flow path to oxidize and decompose dioxins in the gas to oxidize nitric oxide; and the catalyst or carrier with a discharge electrode according to the first invention, Alternatively, a method is provided in which a catalyst block with a discharge electrode according to the second invention is installed in a flow path of a gas containing an organic odor component, and the odor component in the gas is oxidized and decomposed. A third invention according to the present invention relates to a method for decomposing dioxins.

In the method for decomposing dioxins according to the third invention, a granular catalyst having semiconductor characteristics is filled between a pair of electrodes, and a voltage is applied between the electrodes to generate a plasma discharge between the catalyst particles to perform treatment. In this method, dioxins in the exhaust gas are decomposed by flowing the exhaust gas through a catalyst packed bed.

The above-mentioned exhaust gas often contains nitrogen oxides and hydrocarbons together with dioxins, for example, such as gas emitted from a combustion device such as a garbage incinerator.

The above catalyst has photocatalytic activity, for example, a particulate catalyst of an oxide exhibiting semiconductor properties such as titania, zinc oxide, iron oxide, or a catalyst obtained by coating a thin layer of photocatalytically active titania on a tantan titania carrier. Is preferably used.

Preferably, the voltage is applied intermittently at high frequencies, for example at a frequency of 40 Hz to 10 MHz. The electric field strength between the pair of electrodes is preferably between 0.5 and 50 K VZ cm.

The implementation of the method, simultaneously with the decomposition of Daiokishi emissions such, N 0 in the exhaust gas is converted to N 0 _2, and / or hydrocarbons can be converted into C 0 _2.

The dioxin decomposition apparatus according to the third invention is an exhaust gas flue. A pair of electrodes, a catalyst-packed bed provided between the pair of electrodes and comprising a granular catalyst exhibiting semiconductor characteristics, and a power supply for generating a plasma discharge between the catalyst particles by applying a voltage between the electrodes. It generates ultraviolet rays by plasma discharge to excite the photocatalyst and decompose dioxins in the exhaust gas flowing through the catalyst packed bed.

It is preferable to attach a dust removal device (eg, a bag filter) upstream of the pair of electrodes in the flue gas flue, and a denitration device (eg, a denitration device using ammonia as a reducing agent) downstream of the pair of electrodes.

The applied voltage is a so-called electric field strength required for space discharge, ie, an X electrode interval, and is set so that the electric field strength between a pair of electrodes is 0.5 to 50 KVZcm. However, a voltage higher or lower than the above value may be used for the purpose of adjusting the discharge amount, the ultraviolet light emission amount, or the like. The lower limit of the applied voltage is the voltage at which plasma discharge is possible, and varies depending on the type, shape, and state of the filled semiconductor particles, as well as the composition and temperature of the atmosphere gas. The upper limit of the applied voltage is the starting value of the arc discharge, and changes mainly depending on the frequency of the applied voltage.

The wavelength of the ultraviolet light is determined by the composition of the semiconductor catalyst particles filled between the electrodes and the atmosphere gas. When the semiconductor catalyst is anatase titania and the atmosphere is air, the wavelength of ultraviolet light is from 300 to 350 nm, which is a wavelength band desired for a titania-based photocatalyst.

The luminous efficiency of ultraviolet light is related to the particle size of the semiconductor catalyst particles.It is thought that the luminous efficiency will increase if the frequency of interparticle gaps of 1 time or more of the wavelength of ultraviolet light is high in the discharge process, but it is not clear at present . If the gap between particles is too wide, the discharge becomes a so-called space discharge, and the luminous efficiency and wavelength are considered to be greatly affected by the atmospheric gas. This is undesirable in terms of controlling ultraviolet light.

The bed filled with semiconductor catalyst particles in which the plasma discharge continues has a strong oxidation catalytic activity, and oxidizes most of the inorganic and organic compounds flowing through the packed bed at a low temperature of 200 ° C. or lower.

For example, air containing trace amounts of dioxins of less than 1 ng / m ³ (such as 4-dioxin / dioxin) flows almost completely at 150 ° C by flowing through the above-mentioned packed bed of semiconductor catalyst particles. Can be oxidatively decomposed.

Also, if circulating air containing N 0 follows 1 0 0 ppm to semiconductor catalyst charge Hamayuka, Ru can convert N 0 to N 0 _2. The conversion can be arbitrarily controlled by the applied voltage and the frequency.

When the purpose is to oxidize a general compound, titania is preferable as the semiconductor catalyst. If this titania crystal is used as an anatase and imparts photocatalytic activity, it will emit ultraviolet light in one part while absorbing ultraviolet light in another part, and exhibit its function as a photocatalyst. And discharge energy can be used effectively. However, the most suitable semiconductor catalyst can be selected depending on the target reaction, and the semiconductor catalyst is not limited to titania.

In addition, when oxidizing a trace amount of dioxin of 1 ng Zm ³ or less, the semiconductor catalyst is modified with a transition metal, an alkali metal, an alkaline earth metal or an oxide thereof, and the dioxin is oxidized. It is effective to use the one with added kind of adsorptivity. Since the discharge state changes when dust in the gas accumulates on the packed bed of semiconductor catalyst particles, it is desirable to install a dust filter such as a bag filter upstream of the dioxins decomposer according to the third invention. According to the first and second inventions, for example, a catalyst with a discharge electrode having a novel structure, which is suitably used for a catalytic reaction for purifying exhaust gas from a garbage incinerator, various boilers, a diesel engine, or the like, is provided. Can provide a catalyst support.

If the catalyst having the structure according to the second aspect of the present invention is used, the ultraviolet rays generated by the catalyst with electrodes effectively act on the activation of ordinary photocatalysts. The photocatalyst also plays the role of a spacer to provide the necessary gap between the catalysts with electrodes.

According to the third invention, a voltage is applied between the pair of electrodes to generate plasma discharge between the catalyst particles, and to uniformly generate ultraviolet light from the surface of the catalyst particle particles or in the vicinity thereof, thereby exhibiting photocatalytic activity. In addition, dioxins in exhaust gas can be decomposed at a high decomposition rate in a compact reactor. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a plan view showing an example of a comb-shaped electrode pattern. FIG. 2 is a front and back perspective view showing a form in which comb-shaped electrodes are provided on both front and back surfaces of a plate catalyst.

FIG. 3 is a plan view showing an example of a catalyst with a discharge electrode.

FIG. 4 is a graph showing the relationship between the reaction temperature and the NO oxidation rate. Figure 5 is a graph showing the relationship between the reaction temperature and the decomposition rate of o-closed toluene.

FIG. 6 (a) is a plan view of a catalyst block with a discharge electrode, FIG. 6 (b) is a front view thereof, and FIG. 6 (c) is a vertical cross-sectional view thereof. FIG. 7 is a cross-sectional view showing the connection state between the front electrodes of the catalyst with electrodes.

FIG. 8 (a) is a plan view showing a corrugated carrier for photocatalyst, and FIG. 8 (b) is a side view thereof. FIG. 9 is a front and back perspective view showing a form in which comb-shaped electrodes are provided on both front and back surfaces of a catalyst with a plate electrode.

FIG. 10 (a) is a front view showing a catalyst block with a discharge electrode for testing, and FIG. 10 (b) is a vertical cross-sectional view thereof.

FIG. 11 is a schematic diagram showing a reaction tester.

Figure 12 is a graph showing the relationship between the reaction temperature and the N 2 O oxidation reaction rate.

Figure 13 is a graph showing the relationship between the reaction temperature and the 0-closed toluene decomposition reaction rate.

FIG. 14 is a front and back perspective view showing a state in which comb-shaped electrodes are provided on both front and back surfaces of a plate catalyst.

Figure 15 is a perspective view of a catalyst block with a discharge electrode.

Figure 16 is a graph showing the relationship between discharge power and oxidation rate. Figure 17 is a graph showing the relationship between discharge power and oxidation rate. Figure 18 is a graph showing the relationship between concentration and oxidation rate.

Figure 19 is a graph showing the relationship between discharge power and oxidation rate. Figure 20 is a graph showing the relationship between discharge power and oxidation rate. FIG. 21 (a) is a partially cutaway front view showing a plasma discharge decomposition reactor, and FIG. 21 (b) is a cross-sectional view taken along line b—b of FIG. 21 (a). BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention will be described specifically with reference to examples. The first to third embodiments correspond to the first invention, the fourth to eighth embodiments correspond to the second invention, and the ninth embodiment corresponds to the third invention.

Example 1

The surface of a photocatalyst sheet (manufactured by Nippon Inorganic Co., Ltd.) containing titania as a catalytic substance is coated on a paste-like conductive ink containing silver (Noritake).

Three (Company Limited) was screen-printed in the pattern shown in Fig. 1. The printing paste was cured by heating at 150 ° C. for 1 hour in air. Thus, a comb-shaped surface electrode (2) was formed on the surface of the photocatalyst sheet.

Next, on the back of the sheet, the silver paste was placed in the same pattern as the surface electrode, and each comb tooth was opposite to the comb tooth of the surface electrode, and was located at the center just between the comb teeth of the surface electrode. The screen was printed and cured under the same conditions as above. Thus, a comb-shaped back surface electrode (3) was formed on the back surface of the photocatalyst sheet. FIG. 2 is a front and back perspective view of the obtained catalyst having the discharge electrodes on both the front and back surfaces.

Example 2

An AC voltage of 15 KV was applied at 60 Hz to each electrode terminal of the catalyst with a discharge electrode obtained in Example 1, and ultraviolet light (wavelength: 300 to 400 nm) was emitted from the entire surface of the catalyst. It was confirmed.

Example 3

The catalyst with a discharge electrode obtained in Example 1 was cut to obtain a plate-like catalyst (1) shown in FIG. This was sandwiched between Teflon meshes and filled into a quartz glass reaction tube having a gas flow section of 10 mm x 20 mm. The reaction tube is covered with a heater and there is no ultraviolet light from outside. Next, a prepared exhaust gas composed of air containing 100 ppm of NO was passed through the reaction tube at a flow rate of 2.5 liters Z, and an AC voltage of 10 KV was applied at 60 Hz to obtain a reaction temperature of 100 Hz. At ~ 200, the oxidation performance of N 0 was measured by a chemiluminescence method, and the oxidation rate was determined by the following formula [I].

Oxidation rate (%) =

(Inlet concentration – Outlet concentration) / Inlet concentration X 100 0… [I] Also, except that the prepared exhaust gas consisting of NO-containing air was replaced by a prepared exhaust gas consisting of air containing 100 ppm of 0-chlorotoluene (which is generally known as a substitute for dioxins) at 100 ppm. In the same manner as described above, the oxidative decomposability of the 0-closed port toluene was measured by a hydrogen flame decomposition gas chromatograph method, and the oxidative decomposition rate was determined by the above formula [I].

The results obtained are shown in Table 1, FIG. 4 and FIG. As is clear from these, the plate catalyst (1) exhibits high N 0 oxidation property and 0-close toluene decomposition property due to the discharge effect.

Example 4

Nippon Inorganic Ceramic Paper (MCS-05: 0.5 mm thick) is impregnated with Ishihara Sangyo Co., Ltd. titania sol (CSN- 30: solids concentration 32 wt%) and then impregnated. 1 2 0 ° C with and calcined 5 hours at 4 5.0 ° C in air to dry, is found, were fabricated 1 2 0 mm X 5 5 mm titania containing immersion plates were titania content 1 4 0 gZm ² holding .

Five In addition, a ceramic paper (MCS-225: 0.25 mm thick) manufactured by Honsha Co., Ltd. was immersed in the same titania sol as above, and the paper was moistened with a corrugated aluminum sheet. Paste on the template, dry as it is at 120 ° C, peel off the dried product from the template and calcine at 450 ° C for 5 hours, titania content 70 g / m ² as shown in Fig. 8 A 10 O mm x 55 mm titania impregnated corrugated sheet was prepared.

These flat plates and corrugated plates were immersed in a 3% nitric acid aqueous solution for 14 hours, washed in running water for 10 hours, and then dried at 120 ° C to obtain flat and corrugated carriers. Was.

Further, these carriers are immersed in a solution obtained by diluting a titania sol (STS-01: solid content 33 wt%) manufactured by Ishihara Sangyo Co., Ltd. three times with pure water, dried at 120 ° C, and air The resultant was calcined at 300 ° C for 1 hour, at 450 ° C for 1 hour, and at 52 ° C for 1 hour, respectively, to obtain a plate catalyst and a corrugated catalyst having photocatalytic activity.

Next, on the surface of the plate-like catalyst (11), a paste-like conductive ink containing silver (SS-248, manufactured by Nippon Atisson Co., Ltd.) was screened with the pattern shown in FIG. Printed. The printing paste was cured by heating at 150 ° C. for 1 hour in air. Thus, a comb-shaped surface electrode (12) was formed on the surface of the flat catalyst. Then, on the back side of the catalyst, the silver paste described above was placed in the same pattern as the surface electrode, and each comb tooth of the silver paste was opposite to the comb tooth of the surface electrode, and the distance between the comb teeth of the surface electrode was small. Screen printing was performed so as to be located at the center, and cured under the same conditions as above. Thus, a comb-shaped back electrode (13) was formed on the back surface of the plate-like catalyst. FIG. 9 shows a front and back perspective view of the obtained plate catalyst with electrodes (14).

Next, as shown in FIG. 6, a plurality of the plate-like electrode-equipped catalysts (14) and a plurality of the corrugated plate-like photocatalysts (15) are alternately polymerized,

6 These were bundled in an enclosure (16). The enclosing frame (16) is made of ceramic lmm-thick ceramic paper solidified with silica colloid. Both ends in the gas flow direction of the catalyst (14) with a plate-like electrode protrude from the corrugated photocatalyst (15). At one protruding end, each back portion of the comb-shaped surface electrode (12) is connected to each other via three electrode connection shafts (18). That is, as shown in FIG. 7, one end of the catalyst with plate electrode (14) is forcibly fitted into the concave portion on the peripheral side of the conductive connecting member (19), and the center of the connecting member (19) is penetrated. The electrode connection shaft (18) is passed through the hole (20), and the coil-shaped conductive spring (21) is interposed between the adjacent connection members (19) in contact with the connection member (19). I have. At the other protruding end of the catalyst with plate electrode (14), the backs of the comb-shaped back electrode (13) are connected to each other via three electrode connection shafts (18) in the same manner as above. Have been.

Thus, a catalyst block equipped with a discharge electrode was manufactured.

Further, as shown in FIG. 10, two sheets of the above-mentioned catalyst (14) with a plate-like electrode and three sheets of the above-mentioned corrugated photocatalyst (15) were alternately polymerized, and these were bundled in an enclosing frame (16). A catalyst block with a discharge electrode was manufactured. Quartz wool (17) was densely packed in the space between the corrugated photocatalysts (15) on both sides and the surrounding frame (16), so that the prepared exhaust gas did not flow in this portion. Similarly, at the projecting end of the corrugated photocatalyst, the front electrodes and the back electrodes were connected via the electrode connection shaft (18).

The test catalyst block was filled in a reaction tube (23) of a reaction tester (22) shown in FIG. The reaction test machine (22) consists of a stainless steel reaction tube (23), a gas introduction chamber (24) at one end, a gas discharge chamber (25) at the other end, and a constant temperature chamber (26 ). The electrode at one end of the catalyst with a flat electrode, that is, the surface electrode, and the other

7 The electrode at one end, that is, the back electrode, was connected to an AC power supply (27), respectively. The space between the wall of the reaction tube (23) and the surrounding frame of the test catalyst block was sealed with a 3 mm-thick ceramic sheet.

Then, 1 through 0 0 ppm flow Preparation flue gas consisting of air containing N 0 1. 9 N m ³ o'clock in the reaction tester (22), applying an AC voltage 1 0 KV at 6 0 H z At a reaction temperature of 100 to 200 ° C., the oxidation performance (oxidation rate) of NO was measured by a chemiluminescence method.

Oxidative decomposition of toluene was carried out in the same manner as above, except that the prepared exhaust gas consisting of N 0 -containing air was replaced with the prepared exhaust gas consisting of 100 pPm of o-chlorotoluene-containing air. The properties (decomposition rate) were measured by a hydrogen flame decomposition gas chromatograph method.

The obtained results are shown in Table 2, FIG. 12 and FIG. As is evident from these, the catalyst block showed high N 0 oxidizing property and 0-chloro-toluene oxidative decomposition property due to the discharge effect. Table 2

8 Example 5

Nippon Inorganic Co., Ltd. ceramic paper (MCS500: 50 mm x 50 mm, thickness 0.5 mm) is hydrolyzed with titanium isopropoxide, and hydrochloric acid is added to the gel to form a gel. The plate was immersed in the titania acolloid obtained, dried at 120 ° C., and calcined in air at 450 ° C. for 5 hours to obtain a plate (25 g / m ² containing titania photocatalyst). A)

Next, the same operation as in Example 4 was performed using a paste-like conductive ink containing silver (manufactured by Nippon Athison Co., Ltd., SS-24807) on both front and back surfaces of the catalyst plate (A). Then, a comb-shaped surface electrode (32) and a back surface electrode (33) were formed. FIG. 14 shows a front and back perspective view of the obtained photocatalyst flat plate with electrodes (31).

The photocatalyst flat plate (31) was filled in a reaction tube of a reaction tester. The reaction tester was the same as that in Example 4 except that the reaction tube was replaced with an acrylic resin reaction tube having a flow path cross section of 50 mm × 17 mm. Next, a prepared exhaust gas consisting of 150 ppm of NO and 40 ppm of 0-closed toluene-containing moisture-saturated air was passed through a reaction tester at room temperature with a flow rate of 2.5 liters Z and discharged. By changing the conditions, an AC voltage with a frequency of 1000 Hz (sine wave) was applied, the oxidation rate of N 0 was measured by a chemiluminescence method, and the oxidation rate of 0 — The oxidation rate was measured by a chromatographic method, and the oxidation rate was calculated by the formula [I] in Example 3.

The results obtained are shown in Table 3 and FIG. From these results, it is understood that the catalyst is excited by the discharge, and the oxidation of N 2 O and the oxidative decomposition of 0-closed toluene are caused.

9 Table 3

o—CT: Orthochrome mouth toluene

Example 6

The ceramic paper used in Example 5 was immersed in the titania colloid solution used in Example 5, and the paper was stuck in a wet state to an aluminum corrugated template, and kept at 120 ° C as it was. dried and stripped dried product from the mold plate and baked 4 5 0 ° C, 5 hours, as shown in FIG. 1 5, titania component 2 5 g Zm ² possesses 5 0 mm x 5 0 m Chita two An impregnated corrugated sheet (34) was manufactured.

One flat plate (31) was sandwiched between two corrugated plates (34) to produce a sandwich-type catalyst block (35) with a discharge electrode having a discharge electrode as shown in FIG.

This catalyst block was filled in a reaction tube of a reaction tester, and the oxidation rate of N 2 O and the oxidation rate of 0-closed toluene were measured in the same manner as in Example 5.

The results obtained are shown in Table 4 and FIG. From these, the corrugated photocatalyst is also excited by the ultraviolet light generated by the discharge, increasing the oxidation rate of NO and the oxidation rate of 0-closed toluene. Table 4

o—CT: Orthochrome mouth toluene

Example 7

In Example 5, the concentration of N 0 and 0-closed toluene in the prepared exhaust gas was changed, and the other operations were the same as in Example 5, and the change in the oxidation rate was examined.

The results are shown in Table 5 and FIG. When the discharge conditions are fixed, the oxidation rate is almost constant in a normal space discharge (low-temperature plasma discharge), but in this embodiment, the oxidation rate increases with a decrease in the oxide concentration. I understand.

Two Table 5

o—CT: Orthochrome mouth toluene

Example 8

Various metal oxides were impregnated and supported on the titania photocatalyst holding flat plate (31) obtained in Example 5 by an ordinary immersion method to prepare a metal-supported catalyst. Using the same catalyst as in Example 5, the oxidation rates of N 0 and 0-closed toluene were examined.

Table 6, Figure 19 and Figure 20 show the adjusted catalyst specifications and oxidation rates. From these results, it can be seen that the current value with respect to the discharge voltage and the oxidation rate vary depending on the supported metal, but the oxidation rate with respect to the discharge power does not fluctuate significantly.

Table 6

* Methanol ϊ§¾ 0— CT: Orthochrome mouth toluene

Example 9

In Fig. 21, a stainless steel wire mesh (SUS304, 30 mesh, wire diameter 0.2 mm) was placed inside a quartz glass reaction tube (41) having a rectangular channel cross section of 80 mm x 9 mm. A pair of electrodes (42) and (43) each having a size of 160 × 80 × 0.5 mm) were placed facing each other. The spacing between the electrodes was 8 mm. A 1 mm diameter titania photocatalyst spherical particle was filled in the space between the electrodes to form a catalyst packed bed (44). A voltage of 20 KV was applied intermittently at 200 Hz between both electrodes by the power supply (45). Was applied. Ultraviolet light was emitted from the entire catalyst packed bed (44).

The reaction tube (41), through at 1 5 0 ° C air containing N 0 of 1 0 0 ppm at a flow rate of 1 m 3Z sec, was measured oxidation rate to N 0 ₂ in N 0. The average discharge current was varied by changing the intermittent frequency, and the relationship between the average discharge current and the NO oxidation rate (determined by equation [I] in Example 3) was determined. Table 7 shows the results. 7 Average current (a A) NO oxidation rate (%)

11.5 92

10. 0 81

7. 0 58

4.033

1. 0 9

Industrial applicability

The present invention relates to a method and an apparatus for decomposing harmful substances such as dioxins in exhaust gas discharged from refuse incinerators, various boilers, diesel engines and the like by plasma discharge. 'The present invention further relates to a catalyst or a carrier for a catalyst provided with a discharge electrode, and a catalyst or a carrier for a catalyst provided with a discharge electrode, and a photocatalyst disposed between, between, or outside thereof. The present invention relates to a catalyst block provided with a discharge electrode.

Claims

The scope of the claims

1. A catalyst or carrier with a discharge electrode comprising at least one plate-like or sheet-like catalyst or carrier and a dot-shaped or crossed linear or rod-shaped electrode on at least one surface.

2. Electrodes are printed on at least one side of a plate or sheet of catalyst or carrier with a conductive printing ink, sintered metal powder, or metal deposited or sputtered. The catalyst or carrier with a discharge electrode according to claim 1, wherein the catalyst or the carrier is formed by carrying out the coating.

3. The catalyst or carrier with a discharge electrode according to claim 1, wherein the electrode has a comb shape.

4. Make sure that the comb-shaped electrodes are on both sides of the catalyst or carrier, and that the comb teeth on the back electrode are opposite to the comb teeth on the front electrode, and that they are located between the comb teeth on the front electrode. The catalyst or carrier with a discharge electrode according to claim 3, which is formed.

5. The catalyst is carried between the ceramic fibers of the matrix consisting of a plate-shaped or sheet-shaped preform made of ceramic fibers, or the catalyst substance is carried between them. The catalyst with a discharge electrode according to any one of claims 1 to 4, wherein the porous carrier particles are dispersed and held.

6. Porous carrier particles are dispersed and held between matrix ceramic fibers made of a plate-shaped or sheet-shaped preform body made of ceramic fibers. The carrier with a discharge electrode according to any one of claims 1 to 4, wherein the carrier has a discharge electrode.

7. A plurality of plate- or sheet-shaped catalysts or carriers provided with at least one surface of a dot-shaped or intersecting linear or rod-shaped electrode, and a catalyst with these electrodes Ma Or a photocatalyst disposed between and / or on the outside of the carrier, and a catalyst block with a discharge electrode.

8. The catalyst with electrodes and the Z or photocatalyst are placed between the matrix ceramic fibers consisting of a plate-like or sheet-like preform composed of ceramic fibers. 8. The catalyst block with a discharge electrode according to claim 7, wherein the porous carrier particles carrying the particles are dispersed and held.

9. Electrodes are printed on at least one side of a plate or sheet of catalyst or carrier with a conductive printing ink, sintered metal powder, or metal deposited or sputtered. 9. The catalyst block with a discharge electrode according to claim 7, wherein the catalyst block is formed by ringing.

10. The catalyst block with a discharge electrode according to any one of claims 7 to 9, wherein the electrode has a comb shape.

1 1. Comb-shaped electrodes are placed on both the front and back surfaces of the plate or sheet-shaped catalyst or carrier. Each comb tooth of the back electrode is opposite to each comb tooth of the front electrode, and each comb of the front electrode. The catalyst block with a discharge electrode according to claim 10, wherein the catalyst block is formed so as to be located between the teeth.

12. The catalyst block with a discharge electrode according to any one of claims 7 to 11, wherein the photocatalyst is a granular catalyst, a flat plate, or a corrugated plate.

□ o

13. A catalyst block with a discharge electrode according to any one of claims 7 to 12, wherein the catalyst or carrier with an electrode has a flat plate shape and the photocatalyst has a corrugated plate shape.

14. The discharge according to any one of claims 7 to 12, wherein each end of the plate-shaped catalyst or carrier with electrodes protrudes from the corrugated photocatalyst, and each electrode is connected at the protruding end. Touch with electrode Medium block.

1 5. A voltage of 3 to 50 KV per 10 mm is applied between the pair of electrodes of the catalyst or carrier with electrodes at 0.04 to 200 KHz, and the catalyst or carrier is applied between both electrodes. A catalyst or carrier with a discharge electrode according to any one of claims 1 to 6, or a catalyst or carrier with a discharge electrode according to any one of claims 7 to 14, wherein the catalyst or carrier with an electrode is activated by causing a discharge through the catalyst. How to use the catalyst block with discharge electrode described.

1 6. The catalyst or carrier with a discharge electrode according to any one of claims 1 to 6, or the catalyst block with a discharge electrode according to any one of claims 7 to 14 in a gas flow path. A voltage of 3 to 50 KV is applied between the pair of electrodes at 0.04 to 200 KHz per 10 mm between electrodes, and a catalyst or carrier is applied between the two electrodes. A gas catalytic reaction method in which a catalyst or carrier with electrodes is activated by electric discharge, and the target component in the gas is contact-reacted.

17. The catalytic reaction method according to claim 16, wherein the gas is a combustion exhaust gas, and oxidizes and decomposes dioxins in the gas to oxidize nitric oxide.

18. The catalytic reaction method according to claim 16, wherein the gas is a gas containing an organic odor component, and oxidizes and decomposes the odor component in the gas.

1 9. A granular catalyst exhibiting semiconductor characteristics is filled between a pair of electrodes, a voltage is applied between the electrodes to generate plasma discharge between the catalyst particles, and the exhaust gas to be treated flows through the catalyst packed bed and is discharged. A method for decomposing dioxins by plasma discharge that decomposes dioxins in gas.

20. The method according to claim 19, wherein the catalyst has photocatalytic activity. Degradation method of oxins.

21. The method for decomposing dioxins according to claim 19, wherein the catalyst is a titania-based catalyst.

22. The method for decomposing dioxins according to claim 19, wherein the catalyst is obtained by coating a thin layer of photocatalytically active titania on a tanase titania carrier.

23. The method for decomposing dioxins according to any one of claims 19 to 22, wherein a voltage is intermittently applied at a high frequency.

24. The dioxins decomposition method according to claim 23, wherein the voltage is applied intermittently at a frequency of 40 Hz to 10 MHz.

25. The method for decomposing dioxins according to any one of claims 19 to 24, wherein the electric field intensity between the pair of electrodes is 0.5 to 50 KVZcm.

2 6. At the same time, Daiokishi emissions such removal method according to NO in the exhaust gas to one of the請Motomeko 1 9-2 5 for converting the N 0 _2.

27. The dioxins removal method according to any one of claims 19 to 26, wherein the hydrocarbons in the exhaust gas are simultaneously converted into carbon dioxide.

2 8. A pair of electrodes provided in the exhaust gas flue, a catalyst packed bed made of a granular catalyst exhibiting semiconductor properties provided between the pair of electrodes, and a voltage applied between the electrodes to form a space between the catalyst particles. A dioxin decomposer using plasma discharge, which consists of a power supply that generates plasma discharge, generates ultraviolet light by plasma discharge to excite the photocatalyst, and decomposes dioxins in exhaust gas flowing through the catalyst packed bed.

29. The dioxin decomposer according to claim 28, wherein a dust remover is provided upstream of the pair of electrodes in the exhaust gas flue.

0. The dioxin decomposition apparatus according to claim 28 or 29, wherein a denitration apparatus is provided downstream of the pair of electrodes in the exhaust gas flue.